Adaptations in beta-adrenergic cardiovascular responses to training in older women

To determine whether endurance exercise training can alter the beta -adrene rgic-stimulated inotropic response in older women, we studied 10 postmenopa usal healthy women (65.4 +/- 0.9 yr old) who exercised for 11 mo. Left vent ricular (LV) function was evaluated with two-dimensional echocardiography d uring,infusion of isoproterenol after atropine. Maximal O-2 consumption inc reased 23% in response to training (from 1.35 +/- 0.06 to 1.66 +/- 0.07 1/m in; P = 0.004). Training had no effect on baseline LV function, end-diastol ic diameter, LV wall thickness, or LV mass. The increase in LV systolic fun ction in response to isoproterenol was unaffected by training. Furthermore, neither the systolic shortening-to-end-systolic wall stress relationship n or the end-systolic wall stress-to-end-systolic diameter relationship durin g isoproterenol infusion changed with training. We conclude that older post menopausal women can increase their maximal O-2 consumption with exercise t raining without eccentric LV hypertrophy or enhancement of beta -adrenergic -mediated LV contractile function. These observations provide an explanatio n for the finding that maximal cardiac output and stroke volume are not inc reased in older women in response to training.